The present invention relates to an angle-measuring device in accordance with the preamble of claim 1.
An angle-measuring device of this kind is known from American patent U.S. Pat. No. 3,952,417, in which the sensor parts are each connected to the central part via two legs. These two always form a type of parallelogram structure, in which one leg of one sensor part is pivotably connected to one leg of the other sensor part.
For medical purposes, it is often important to know the pivoting movement of two body parts with respect to one another. Obviously, it is also important for other purposes to know the angle between two parts.
However, there are often obstacles which make it impossible to place the two legs flat against the body parts or other parts to be measured in question.
European Patent Application 0,287,149 proposes a solution to this problem in that the legs are no longer pivotably connected to one another, but rather are attached to one another by means of a flexible strip. Sensitive parts are situated in this strip, and it is possible to use this strip when it does not bear against the body parts or other parts to be measured in question. In this way, obstacles situated in the region of the vertex are circumvented.
The device which is described in European Application 0.287,149 is particularly complicated, and it has been found that after a relatively long period of time it is no longer possible to ensure that the device is sufficiently accurate. Moreover, it is particularly sensitive to damage.
A number of the problems indicated above can be solved using the angle gauge in accordance with American patent U.S. Pat. 3,952,417. However, the travel of this gause, i.e. the angular range which can be measured, is limited. Moreover, this design is complicated and fragile as a result of the use of four external legs.
British patent 2,008,287 has disclosed a loading/unloading arm provided with sensors for determining the angle of the various arm parts. In this patent, one part of the angle-measuring device is permanently fixedly connected to the surrounding area. An angle-measuring sensor is arranged on each of the pivoting arms, at a distance from the pivot point.
The object of the present invention is to provide an angle-measuring device with which a wide range of angles can be covered and which has a comparatively simple design.
This object is achieved in the case of an angle-measuring device as described below.
The fact that the pivot point of the legs coincides with the pivot point of the measurement means results in a considerable structural freedom, with the result that it is possible to design the angle-measuring device in such a manner that a large angle range can be covered.
The movement of the sensor parts can be transmitted in any manner which is known in the prior art. An example which may be mentioned is a mechanical connection, such as a chord connection between the sensor parts and the sensor plate or plates in the event of using a single angle-measuring sensor, In a preferred embodiment, this connection is situated in the pivot point of the two legs which is described above.
It will be understood that instead of the chord connection mentioned here it is possible to use any other connection which is known in the prior art.
Any design which is known in the prior art may be used for the sensor described above. For example, it is possible to use resistance-based sensor plates which transmit a different resistance value on rotation (potentiometer). It is also possible to use a series of light-sensitive diodes and a light source.
However, it is preferred to design the angle-measuring sensor as a capacitative sensor. In this case, the plates of the sensor act as a condenser plate.
It is possible to accommodate at least some of the associated electronics in the housing which is arranged in the region of the pivot point of the two legs. Obviously, it is also possible to arrange another part of the electronics outside the electronic angle-measuring device according to the invention and to provide a wireless connection or a connection with a wire to a device of this kind.
It will be understood that the angle gauge described above has numerous applications both in the medical field and in other fields. In addition to measuring angles, the electronic design of this device makes it particularly easy to calculate radii of curvature and, from this, to determine circumferences and surface areas.